An array antenna, such as for example a reflectarray antenna or a phase-controlled array antenna (also known as a phased array antenna), comprises a set of elementary radiating elements assembled in a one-dimensional or two-dimensional radiating array making it possible to increase the directivity and the gain of the antenna. In reflectarray antennas, the elementary radiating elements of the array often consist of an arrangement of patches and slots whose dimensions vary. The shape of the radiating elements, for example square, circular, hexagonal, is generally fixed and unique for the array. The dimensions of the radiating elements are adjusted so as to obtain a chosen radiation pattern when they are illuminated by a primary source. In phase-controlled array antennas, the distributing of the signal to the radiating elements of the array is done with the aid of a beam-forming distributor.
The elementary radiating elements can consist of a structure with cavity and radiating slots which is mounted on a metal plane or of a planar structure comprising a metal radiating patch printed on the surface of a dielectric substrate mounted on a metal plane, the metal patch possibly comprising one or more slots as represented for example in FIG. 1. The radiating slots can be made of a dielectric material or a composite material such as the superposition of a honeycomb of printed fine dielectric substrates used as a skin of the composite material. However, in order for the antenna to be capable of supporting a space environment, it is necessary to ensure that the phenomena of electrostatic discharges between the radiating elements are minimized.
It is known to minimize the electrostatic discharges on a spacecraft by linking all the electrically conducting external surfaces and all the internal metal elements of the spacecraft to the main metal structure of the craft. For linearly polarized radiating elements, grounding can be achieved without any particular problem by connecting the radiating elements to an external metal grid by a metal wire along an axis of symmetry perpendicular to the direction of polarization.
However, for a radiating array consisting of elementary radiating elements of planar structure with dual polarization, it is necessary to take account of the polarization of the various radiating elements. Indeed, connecting the radiating elements directly together, for example by way of a metal wire, would affect the polarization and the operation of these elements and could destroy the resonances and cause the excitation of other higher modes. Furthermore, in the case of an array antenna, the matching of the radiating elements could be destroyed.